1. Field of the Invention
The present invention relates to a system for cleaning the collecting plates and/or emitting wires in an electrostatic precipitator and, more particularly, to a control system that regulates the operation of rapping or vibrating devices for effectuating such cleaning.
2. State of the Art
Electrostatic precipitators are widely used for removing contaminating particles and droplets from gaseous streams. The typical electrostatic precipitator in large-scale applications includes a housing in which banks of vertically-extending collector electrode plates are disposed such that a dust-laden gaseous stream can pass at relatively high velocity through the housing parallel to the surfaces of the plates. Electrically, the collector plates are connected to ground. Active or emitting electrode wires hang vertically between the banks of collector plates and are electrically charged to as much as minus 45 to 50 thousand volts. In operation, an electric corona discharge from the emitting wires ionizes the neighboring gas molecules which then adhere to the dust particles and carry the same to the collector plates under the influence of electrostatic force.
In conventional practice, the collecting plates are periodically impacted or rapped so that the collected particulates fall by gravity to the floor of the housing for subsequent removal. It is also known to vibrate the emitter wires periodically to discharge any particles therefrom. A recognized problem in this art is to perform the rapping and vibrating functions in an optimal manner. When rapping or vibrating is conducted in a sub-optimal fashion, dislodged particulates are re-entrained in the gaseous stream flowing out of the precipitator. Sometimes puffs of particulates can actually be observed to issue from the precipitator outlet, thereby indicating that the precipitator is operating inefficiently.